The gold at the end is not explained at all. I think the author is just trying to show his interpretation of Japanese culture being too weird or peculiar to him to understand. I think the reason for the gold would have to be simply Mr Ito's appreciation for all the hard work Mr. Harris endured to show Mr Ito all the different attractions. One thing is for sure- I've seen situations like this where some Asians will be generous in a situation similar like this, and the other person just won't get it. It's kind of sad when you think about it.